Hydraulically propelled vehicle

ABSTRACT

An earthworking machine having front and rear traction means and a hydraulic motor for each. The motors are connected in a closed loop parallel circuit with a pump, and one of them drives its traction means through a plural speed transmission. A first valve mechanism divides pump output fluid equally between the motors. An orifice device in the motor-pump circuit allows up to a predetermined small amount of fluid flowing to either motor to be diverted to the other motor. Second valve means in the hydraulic circuit maintains the first valve mechanism effective except at times when the transmission is in other than a low speed working position.

United States Patent [191 Larson 1 1 HYDRAULICALLY PROPELLED VEHICLE[75] Inventor:

[73] Assignee: Raygo, Inc., Minneapolis, Minn.

[22] Filed: Feb. 4, 1974 [21] Appl. No.: 439,528

Roger L. Larson, Waeonia, Minn.

[52] US. Cl. 172/3; 60/420; 180/20;

180/66 R; 172/801; 172/438; 404/103 [51] Int. Cl. AOlb 67/00; A01b 49/02[58] Field of Search 172/2, 3, 63, 801-809,

172/438; 60/420, 468, 484, 494; 180/20, 44 F, 53 R, 66R;404/102,103,117,122

[ 1 June 17, 1975 3,605,583 9/1971 Keppler 404/117 3,641,765 2/1972Hancock ct a1 60/484 3,736,732 6/1973 Jennings et a1 180/44 F X PrimaryExaminer-Edgar S. Burr Assistant E.raminerPaul T. Sewell [57] ABSTRACTAn earthworking machine having front and rear traction means and ahydraulic motor for each. The motors are connected in a closed loopparallel circuit with a pump, and one of them drives its traction meansthrough a plural speed transmission. A first valve mechanism dividespump output fluid equally between the motors. An orifice device in themotorpump circuit allows up to a predetermined small amount of fluidflowing to either motor to be diverted to the other motor. Second valvemeans in the hydraulic circuit maintains the first valve mechanismeffective except at times when the transmission is in other than a lowspeed working position.

4 Claims, 2 Drawing Figures PATENTEDJUN 17 I975 SHEET F'GslsHYDRAULICALLY PROPELLED VEHICLE This invention relates to earth workingvehicles, and has more particular reference to hydrostatically propelledvibratory earth compacting machines.

One such compactor that has recently become available is made by RAYGO,INC. of Minneapolis, Minnesota, and is known in the trade as its Rascal320A. It features a pair of rear traction wheels driven through a twospeed transmission by a first reversible hydraulic motor, and acompacting drum mounted on a yoke at the front of the machine forrotation on a generally transverse axis. The drum, which is of the samediameter as the wheels, is equipped with vibration producing mechanismand it is rotatably driven by a second reversible hydraulic motor. Itthus constitutes the front part of the hydrostatic propulsion means onthe machine.

One of the unusual features of the Rascal 320-A is that it is providedwith a bulldozer blade at its front, ahead of the drum. This enables themachine to move a substantial amount of earth in levelling and scrapingoperations. for example, and at the same time effect compaction of theearth acted upon by the blade, by the drum behind it.

Inasmuch as the levelling blade is carried by the drum yoke, loading ofthe blade during use of the machine exerts force on the drum tending tolift it out of tractive engagement with the ground. This, of course,effects unloading of the drum, and as a result, seriously detracts fromits effectiveness as a combination traction device and compacting tool.

This same phenomenon also prevents the drum and rear wheel tractiondevices from being driven by fluid motors connected in parallel with asingle bidirectional pump. in a closed loop circuit. In that case, thelifting effect of the levelling blade on the drum would merely cause allof the pump output fluid to pass to the more lightly loaded drum motor,producing what is known as drum spin out and loss of vehicle propulsion.

Hence, it is one of the purposes of this invention to provide ahydrostatically driven earth working machine of the character described,wherein an equal ratio flow divider and combiner valve instrumentalityis installed in one side of a closed loop parallel circuit for the twomotors relied upon to drive the drum and rear wheels.

Inasmuch as it is also desirable to transmit driving torque to the rearwheels of the machine through a transmission having a low or workingspeed, and a higher speed for transit, it will be seen that aconventional flow divider can not afford a complete solution to theproblem.

In fact, a further complication which tended to make the wheels drivethe vehicle faster than the drum re sulted from accumulations of stickymud on the wheels. Such material buildup could, at times increase theeffective wheel circumference to a dimension sufficiently greater thanthat of the drum as to cause the latter to act somewhat in the nature ofa drag. It should be here mentioned that material is not allowed tobuild up on the drum. as scraper means continually removes mud and/orother accumulations therefrom during operation of the machine.

With these further problems in mind, it is another object of theinvention to provide a hydrostatically driven compactor such asdescribed, with valve instrumentalities that not only make it possibleto drive the rear wheels through a plural speed transmission, but whichalso automatically overcome the undesirable effects of material buildupon the wheels that would otherwise interfere with the production ofequal propelling rates by the drum and rear wheels of the machine.

More specifically, it is a purpose of this invention to connect thereversible drum and wheel motors of the machine in a closed loopparallel circuit with a bidirectional pump, and to incorporate an equalflow ratio dividing and combining valve in one side of said circuit,along with an orifice device that makes possible diversion of smallportions of the fluid flowing in either branch of the closed loopcircuit at one side thereof to the other branch of the circuit at saidside thereof, to thus compensate for any change in the effectivediameter of the wheels that may occur due to material buildup thereon.

It is also a more specific object of the invention to provide in theaforesaid closed loop parallel motor circuit, at one side thereof, avalve device which, in one position, renders the equal ratio flowdivider and combiner valve mechanism effective, and which, in anotherposition, acts to nullify the effect of said valve mechanism to therebyallow faster propulsion of the machine in a second speed position of thetransmission.

Still another object of the invention resides in the provision of avalve device such as described in the preceding paragraph, which is ofthe electromagnetic type, and which can be actuated to its positioncancelling the effect of the divider-combiner valve mechanism as aconsequence of shifting of the transmission out of its working speed toa higher speed ratio.

With these observations and objectives in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings, which exemplify theinvention, it being understood that changes may be made in the specificapparatus disclosed herein without departing from the essentials of theinvention set forth in the appended claims.

The accompanying drawings illustrate one complete example of anembodiment of the invention constructed according to the best mode sofar devised for the practical application of the principles thereof, andin which:

FIG. 1 is a diagrammatic view showing the hydrostatically propelledtraction means of a compacting machine embodying the principles of thisinvention; and

FIG. 2 is a diagram wherein graphic symbols illustrate the hydrauliccircuitry for the hydrostatic propulsion means of this invention.

Referring now more particularly to the accompanying drawings, thenumeral 5 generally designates a vibratory earth compacting machine ofthe type manufactured by RAYGO, INC. and known as its Rascal 320-A, Themachine is characterized by front and rear traction means 6 and 7,respectively; reversible hydraulic motors 8 and 9 drivingly connectedwith the front and rear traction means, respectively; and abidirectional piston type pump 10 to supply fluid under pressure to themotors. The pump is driven by an internal combustion engine 11, whichmay be of the Diesel variety, through a clutch l2 and a drive box 13.

The rear traction means 7 is here shown as comprising a pair oflaterally spaced wheels 14 carried by an axle structure 15 and drivenfrom the hydraulic motor 9 through a two speed transmission 16.

The front traction means 6 comprises a vibratory drum of the samediameter as the wheels, and which is rotatably carried by a yoke havingarms indicated at 18, that embrace the opposite ends of the drum. Thesearms carry the bearings, not shown, in which the drum is rotatablyjournalled. Hydraulic motor driven vibration producing means is mountedinside the drum.

For purposes of illustration, the spacing between the wheels 14 has beenexaggerated, as in the actual machine, they are spaced apart a distanceless than the axial dimension of the drum 6. Also for purposes ofillustration, the multiplicity of tamping feet which project from theexterior of the drum have been omitted.

One of the chief characteristics of the machine herein concerned, isthat it is provided with a scraper or levelling blade located ahead ofthe drum 6. The blade is supported from the yoke arms 18, as by links21, and it is raised and lowered hydraulically by double actingcylinders, not shown, having one end pivotally mounted on the yoke armsand having piston rods connecting with brackets on the rear of theblade, as indicated at 22.

A lever 24 which is accessible to an operator of the machine, enablesthe transmission 16 to be shifted into low and high speed positions. Thelow speed position is the one selected for levelling and compactingoperations of the machine, while the high speed position allows themachine to be more quickly driven from one work zone to another.

The presence of the plural speed transmission 16 causes one of theproblems which are solved by this invention. The scraper blade 20 aheadof the vibrator drum causes another.

These problems can be best appreciated from a consideration of the FIG.2 hydraulic diagram. This diagram illustrates by means of graphicsymbols, that the drum and wheel drive motors 8 and 9, respectively, areconnected in a closed loop parallel circuit with the bidirectional pump10.

For this purpose, one of the ports of the drum motor 8 is connected withone of the ports 31 of the wheel drive motor 9, as by means of a duct 32having a branch 33 connected with one of the work ports 34 of the pump.Accordingly, the ducts 32 and 33 comprise one side of the closed loopparallel pump-motor circuit. The other side of the circuit comprises aduct 36 having its ends connected to the remaining ports 37 and 38 ofthe motors 8 and 9, respectively, and having a branch 39 connecting withthe other work port 40 of the pump.

A characteristic of the closed loop parallel circuit thus far described,is that pressure fluid from either work port of the pump will flow towhichever hydraulic motor 8 or 9 is more lightly loaded, and will bypassthe more heavily loaded motor. The propulsive effort will be dissipated,therefore, whenever the scraper or levelling blade 20 ahead of thecompacting drum 6 exerts upward force on the drum sufficient toseriously reduce its tractive relationship to the ground over which themachine is travelling. At such times, all of the pump output fluid willflow to the hydraulic motor 8 for the then unloaded compacting drum 6,in bypass relation to the wheel drive motor 9. This produces what isknown as drum spin out; and the machine stalls whenever such spin outoccurs.

By to this invention, the danger of such "spin out" of the drum iseliminated through the provision of a valve instrumentality 42,connected in one side of the closed loop hydraulic circuit. The maincomponent of the valve instrumentality 42 comprises an equal ration flowdivider-combiner valve mechanism 43. It has a pair of motor ports 44 and45 which are connected with the ports 37 and 38 of the drum and wheelmotors 8 and 9, respectively, by the duct 36. It also has a pump port 47which is connected with the work port 40 of the pump by the branch 39 ofduct 36.

The flow divider valve mechanism 43 is of conventional construction and,for example, can be one such as manufactured by Fluid Controls, Inc. andcharacterized by a pair of pressure compensated plungers, not shown, toregulate flow of fluid in either direction between its pump port 47 andits motor ports 44, 45.

As is well known, the equal ratio flow dividercombiner valve mechanism43 will function with reasonable accuracy to divide pressure fluidissuing from work port 40 of the pump, for example, into equal volumesfor operation of the drum and wheel motors at the desired speeds.Moreover, it will perform this function regardless of whether or not thecompactor drum is fully loaded. This is to say that even though theupward force exerted on the drum by the levelling blade maysubstantially reduce the loading thereof, the rear wheel motor 9 willstill receive its share of pump output fluid, and there will be nopossibility of drum spin out to interfere with propulsion of themachine.

The equal ratio flow dividercombiner valve operates in the same way whenthe motors 8 and 9 are being driven in the opposite direction by thepump. In that case, however, the flow of return fluid from the motors 8and 9 to the work port 40 of the pump is controlled by the equal ratiocombining action of the valve mechanism 43.

The valve instrumentality 42 also features a pressure compensatedorifice device 50 which is shown as connected across the ports 37 and 38of the two motors through the ends of the ducts 36 leading thereto. Theorifice device 50 can be said to perform a speed control function in thesense that it acts to automatically compensate for the changingvolumetric efficiency of the two motors 8 and 9 due to increase in therolling radius of the wheels 14 by the build up of material thereonoccurring whenever the machine is operated in sticky mud.

By way of example, if a substantially small quantity of mud should buildup on the wheels 14, they would tend to drive the machine at a fasterrate than the drum, due to the increase in wheel circumference.

A scraping device, not shown, prevents all but an insignificant amountof material build up on the drum. Hence, the orifice device is providedprimarily because of build up on the rear wheels.

With the orifice device 50 in one side of the closed loop pump-motorcircuit, however, a small amount of the pressure fluid will be allowedto pass between the ducts connecting the pump with the propel motors 8and 9 at one side of the closed loop parallel circuit. As shown, theorifice device can be connected across the end portions of the duct 36leading to the motor ports 37 and 38.

Depending upon changing fluid pressure conditions in the duct 36 asmaterial builds up on the wheels, the orifice device 50 will be causedto open, for example,

to allow up to a maximum of 3 gallons per minute of fluid to flowtherethrough from one end of the duct 36 to the other thereof.

An equally important component in the circuit is a two positionelectromagnetic valve 53 which. in effect, removes the equal ratio flowdivider valve 43 from the circuit any time the transmission 16 isshifted out of its low, or work speed position. Like the orifice device50, the valve 53 is connected across the end portions of the duct 36 ata location between the propel motors (8 and 9) and the equal ratio flowdivider 43.

In its position shown, the valve 53 establishes communication betweenthe ports 37 and 38 of the propel motors. thus permitting supply fluidflowing to those motor ports from the pump, to pass to the motors inwhatever proportions are necessary as determined by the ground as adifferential. This, of course, allows the machine to travel in second orhigher speed, and makes possible the use of a plural speed transmissionthrough which driving torque is transmitted to the rear wheels from thewheel propel motor 9.

The solenoid valve 53 can be of the normally open type connecting motorports 37 and 38 as shown, in which case it is actuated to its closedposition upon energization of its solenoid 54. Solenoid 54 is in anenergizing circuit which includes a switch 55. The switch can be closedto complete the energizing circuit for the solenoid 54 in consequence ofactuation of the shift lever 24 to place the transmission in its lowspeed working position. as indicated in dotted lines in FIG. 2. Anysuitable way of effecting such closure of switch 55 will suffice, as forexample, a direct link connection 56 between the shift lever 24 and themovable contactor of the switch.

From the foregoing description, together with the accompanying drawings,it will by readily apparent to those skilled in the art that thisinvention provides an earth working machine in which improvedhydrostatic propulsion means makes possible advantages which wereherethereto unattainable.

Those skilled in the art will appreciate that the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

The invention is defined by the following claims I claim:

1. In an earth working machine having traction wheels at its rear and acompacting drum and leveling blade at its front, the compacting drumbeing power driven to coact with the traction wheels in effectingpropulsion of the machine and being rotatably connected with a yoke thatprojects forwardly from the chassis of the machine, and the levelingblade being mounted on said yoke ahead of the compacting drum formaximum effectiveness, said machine being characterized by an improvedpropulsion system which assures continued propulsion of the machineregardless of diminished traction between the drum and ground due to theinevitable upward force on the yoke resulting from loading of theleveling blade during use thereof,

and which improved propulsion system comprises:

A. a power driven bidirectional hydraulic pump;

B. a reversible hydraulic motor drivingly connected with the drum;

C. a second reversible hydraulic motor drivingly con nected with thetraction wheels;

5 said motors; and

E. an equal ratio flow divider-combiner valve mechanism connected in oneside of said closed loop hydraulic circuit to divide the pressurefluid-issuing from the pump and flowing to the hydraulic motors intosubstantially equal volumes so that reduction in the load on thehydraulic motor driving the drum and resulting from loss of tractionbetween the drum and ground as a consequence of increased loading of theleveling blade will not diminish traction at the rear wheels of themachine.

2. The invention defined by claim 1 further characterized by a pressurecompensated orifice device connected in said hydraulic circuit inparallel with the equal ratio flow divider-combiner valve mechanism,

said orifice device modifying the fixed ratio aspect of the flowdivider-combiner valve mechanism by allowing a predetermined maximumamount of flow to pass between the supply lines leading to the twohydraulic motors to thereby compensate for change in the volumetricefficiency of the motors resulting from an increase in the rollingradius of the traction wheels by buildup of material thereon.

3. The invention defined by claim 1, wherein the hydraulic motor drivingthe rear traction wheels is drivingly connected therewith through aplural speed transmission having operator-controlled gear shifting meansby which the transmission can be shifted from one to another ofitsspeeds, and further characterized by a bypass passage connected in thehydraulic circuit in parallel with said equal ratio flowdivider-combiner valve mechanism to communicate said supply linesleading to the hydraulic motors when said passage is open and therebynulify the effect of the equal ratio flow dividercombiner valvemechanism on the functioning of the system but when closed having noaffect thereon;

a valve in said bypass passage;

said valve being closed when the plural speed transmission is in its lowspeed mode; and

means operable in response to actuation of the operator-controlled gearshifting means in taking the transmission out of its low speed mode, toeffect opening of said valve in the bypass passage.

4. In combination with an earth working machine having a compacting drumat its front, and wheels at its rear:

A. a yoke having arms embracing the opposite axial ends of the drum andin which the drum is journailed for rotation on a transverse axis;

B. a levelling blade carried by the yoke arms and located ahead of thedrum;

C. means for transmitting rotation to the drum comprising a firstreversible fluid motor having a pair of ports;

D. means for transmitting rotation to the wheels comprising a secondreversible fluid motor having a pair of ports, and plural speedtransmission means drivingly connecting the wheels with said secondmotor;

E. a bidirectional pump having a pair of work ports;

F. means connecting said motors in a closed loop parallel circuit withthe pump, comprising a first duct connecting with one of each of themotor ports and having a branch connecting with one of the work 2. anorifice device through which the ports of said ports of the pump, and asecond duct connecting one motor are connectible with one another,

the other pump port with the other of said motor 3. and a valvemechanism movable from a first poports; sition communicating the portsof said one motor G. valve instrumentalities connecting with said firstto a second position disrupting said last named duct and comprisingcommunication;

1. an equal ratio flow divider valve having its inlet H. and means toeffect actuation ofsaid valve mechaconnected with one pump through saidbranch of nism to said second position thereof in consesaid first duct,and having a pair of outlets conquence of actuation of the transmissionmeans to nected with the ports of said one motor through 10 a low speedposition.

said first duct,

1. In an earth working machine having traction wheels at its rear and acompacting drum and leveling blade at its front, the compacting drumbeing power driven to coact with the traction wheels in effectingpropulsion of the machine and being rotatably connected with a yoke thatprojects forwardly from the chassis of the machine, and the levelingblade being mounted on said yoke ahead of the compacting drum formaximum effectiveness, said machine being characterized by an improvedpropulsion system which assures continued propulsion of the machineregardless of diminished traction between the drum and ground due to theinevitable upward force on the yoke resulting from loading of theleveling blade during use thereof, and which improved propulsion systemcomprises: A. a power driven bidirectional hydraulic pump; B. areversible hydraulic motor drivingly connected with the drum; C. asecond reversible hydraulic motor drivingly connected with the tractionwheels; D. a closed loop parallel hydraulic circuit including supplylines leading to the hydraulic motors connecting the pump with thehydraulic motors and through which pressure fluid is delivered to bothof said motors; and E. an equal ratio flow divider-combiner valvemechanism connected in one side of said closed loop hydraulic circuit todivide the pressure fluid issuing from the pump and flowing to thehydraulic motors into substantially equal volumes so that reduction inthe load on the hydraulic motor driving the drum and resulting from lossof traction between the drum and ground as a consequence of increasedloading of the leveling blade will not diminish traction at the rearwheels of the machine.
 2. The invention defined by claim 1 furthercharacterized by a pressure compensated orifice device connected in saidhydraulic circuit in parallel with the equal ratio flow divider-combinervalve mechanism, said orifice device modifying the fixed ratio aspect ofthe flow divider-combiner valve mechanism by allowing a predeterminedmaximum amount of flow to pass between the supply lines leading to thetwo hydraulic motors to thereby compensate for change in the volumetricefficiency of the motors resulting from an increase in the rollingradius of the traction wheels by buildup of material thereon.
 2. anorifice device through which the ports of said one motor are connectiblewith one another,
 3. and a valve mechanism movable from a first positioncommunicating the ports of said one motor to a second positiondisrupting said last named communication; H. and means to effectactuation of said valve mechanism to said second position thereof inconsequence of actuation of the transmission means to a low speedposition.
 3. The invention defined by claim 1, wherein the hydraulicmotor driving the rear traction wheels is drivingly connected therewiththrough a plural speed transmission having operator-controlled gearshifting means by which the transmission can be shifted from one toanother of its speeds, and further characterized by a bypass passageconnected in the hydraulic circuit in parallel with said equal raTioflow divider-combiner valve mechanism to communicate said supply linesleading to the hydraulic motors when said passage is open and therebynulify the effect of the equal ratio flow divider-combiner valvemechanism on the functioning of the system but when closed having noaffect thereon; a valve in said bypass passage; said valve being closedwhen the plural speed transmission is in its low speed mode; and meansoperable in response to actuation of the operator-controlled gearshifting means in taking the transmission out of its low speed mode, toeffect opening of said valve in the bypass passage.
 4. In combinationwith an earth working machine having a compacting drum at its front, andwheels at its rear: A. a yoke having arms embracing the opposite axialends of the drum and in which the drum is journalled for rotation on atransverse axis; B. a levelling blade carried by the yoke arms andlocated ahead of the drum; C. means for transmitting rotation to thedrum comprising a first reversible fluid motor having a pair of ports;D. means for transmitting rotation to the wheels comprising a secondreversible fluid motor having a pair of ports, and plural speedtransmission means drivingly connecting the wheels with said secondmotor; E. a bidirectional pump having a pair of work ports; F. meansconnecting said motors in a closed loop parallel circuit with the pump,comprising a first duct connecting with one of each of the motor portsand having a branch connecting with one of the work ports of the pump,and a second duct connecting the other pump port with the other of saidmotor ports; G. valve instrumentalities connecting with said first ductand comprising